Mats of glass fibers can be made by several different processes. The general type of glass fiber mat making machinery with which we are concerned is generally shown in U.S. Pat. No. 2,736,676, U.S. Pat. No. 3,599,848 and U.S. Pat. No. 3,676,095. In the process in which the present invention has particular advantages, molten streams of glass fibers are pulled into very fine filaments by a revolving drum over which the filaments are wrapped. The filaments are discharged tangentially downwardly from the revolving drum onto a moving foraminous conveyor or moving foraminous collection surface with moves the mat that is laid down on the conveyor through subsequent operations where a binder is applied and through an oven where the binder is cured. The filaments which are discharged onto the conveyor are thrown from side to side across the conveyor by the impingement of alternate lateral blasts of air. The lineal speed of the strand is many times the speed at which the strand traverses the conveyor, so that the strand assumes a looped condition on the conveyor. After the molten streams of glass are attenuated into filaments and before these filaments reach the revolving drum, they are coated with an aqueous lubricating material and are brought together in the from of a strand. This aqueous material is generally referred to as a sizing which functions to prevent the fibers from breaking as they pass around guide surfaces and are pulled over the surface of the revolving drum. The sizing also must perform the function of preparing the surface of the fibers for proper wet-out by a binder material which is subsequently applied to the mat formed on the conveyor for the purpose of holding the fibers together.
Men working with apparatus which functions according to the process above described, have tried solutions of many materials including conventional starches and cationic lubricants, such as the reaction product of tetraethylene pentamine and stearic acid in a molar ratio of 1 to 1.8 as a lubricant to protect the fibers from abrasion. Some of these sizings, while providing proper lubrication to the fibers, have prevented a proper random looping of the strand on the conveyor. Others have caused the fibers to wrap around the revolving drum to thereby disrupt the process. Still others have caused inefficiency in operation of the apparatus, especially in respect to an objectionable build-up of solids from the sizing on the apparatus. Some of the materials that have been applied heretofore have produced a mat whose strength crosswise of the mat was appreciably greater then the strength lengthwise of the mat. Other materials provide for lengthwise and crosswise strength characteristics of the mat to be of the same magnitude. However, until the present invention, it has not been possible to prevent build-up of sizing solids on this apparatus, particularly the revolving drum.
A principal objective of the present invention is the improvement of the above described process, to achieve more efficient and sustained operation in the processing of glass fiber mat without adversely affecting other desirable properties of the strand and the mat.